Cylindrical battery and method and device for manufacturing thereof

ABSTRACT

In the process of manufacturing a cylindrical battery, when a tubular separator ( 3 ) and bottom separator ( 5 ) are inserted into a battery casing ( 1 ) in which are accommodated positive electrode mixture pellets ( 2 ), by inserting the bottom separator ( 5 ) such that it is pushed into the battery casing ( 1 ) at the leading end of the tubular separator ( 3 ), the peripheral portion of the bottom separator ( 5 ) is raised up, so that both separators ( 3,5 ) are inserted into the battery casing ( 1 ) in a condition with the leading end of the tubular separator ( 3 ) surrounded from the outside by this peripheral raised-up portion.

TECHNICAL FIELD

The present invention related to a cylindrical battery wherein dischargeperformance and reliability are enhanced by improving the mountingstructure of the separator that seperates the positive electrodematerial and negative electrode material within the battery, and amethod and device for manufacturing such a cylindrical battery.

BACKGROUND ART

FIG. 9 is a partially sectioned front view showing a prior artconstruction of an alkaline dry battery 30 as one example of acylindrical battery. A battery casing 1 of cylindrical shape having abottom is integrally provided with a positive electrode projection 6constituting the positive electrode terminal of the battery, in themiddle of its bottom face. This battery casing 1 accommodates positiveelectrode mixture pellets 2 and a negative electrode gel 4 in theinterior thereof, with a tubular separator 35 interposed therebetween.The open end of battery casing 1 is sealed by a sealing plate 7 made ofresin, a negative electrode terminal 8 connected to a negative electrodecurrent collector 9 being mounted on this sealing plate 7. Tubularseparator 35 is formed in cylindrical shape by winding separator paperinto a roll, a portion at the bottom end thereof being folded inwardscontacting the bottom face of the battery casing 1 and constituting abottom part 35 a. Since the middle portion of this bottom part 35 a isopen, a circular bottom separator 36 having a larger diameter than theinternal diameter of tubular separator 35 is inserted within tubularseparator 35 in order to cover this aperture portion and thereby preventinternal short circuits between negative electrode gel 4 and batterycasing 1. Furthermore, a step 1 a is provided in the bottom face ofbattery casing 1, to absorb even if only to a small extent, thethickness of the bottom part 35 a of tubular separator 35 and bottomseparator 36, so as to avoid, as far as possible, offset in the verticaldirection of the reaction surfaces where the negative electrode gel 4and positive electrode mixture pellets 2 face each other.

The mounting of tubular separator 35 and bottom separator 36 in themanufacturing step of this alkaline dry battery 30 is performed by amanufacturing device shown in FIGS. 10A-10D.

In FIG. 10A, a battery feed jig 15 holding a battery casing 1 is moveddirectly below a winding rod 33 of a tubular separator installationdevice 32, after positive electrode mixture pellets 2 have beenaccommodated in battery casing 1 in a previous step, not shown. Thediameter of winding rod 33 below step 38 is formed smaller than thediameter thereabove by an amount corresponding to the thickness oftubular separator 35, and this winding rod is supported such as to berotated in the forwards and reverse directions and can be raised andlowered. When separator paper, that has been cut to prescribeddimensions, is supplied to the gap between winding rod 33 and windingguides 34, winding rod 33 is rotated in the forwards direction, and theseparator paper is wound about the portion of winding rod 33 lower thanstep 38. In this process, slackness in winding is avoided by pressingthe separator paper on to winding rod 33 by means of winding rollers 37.In this way, a tubular separator 35 is formed on winding rod 33 asshown, by winding the separator paper about winding rod 33 a prescribednumber of times.

Next, as shown in FIG. 10B, winding rollers 37 are retracted fromwinding rod 33, winding rod 33 is lowered, and battery feed jig 15 israised, so that winding rod 33 with tubular separator 35 wound thereonis inserted into battery casing 1. At this point the tubular separator35, when inserted into battery casing 1, is released from the restraintapplied by winding guides 34, so it increases its winding radius byspringing back of its own accord so that it is in tight contact withpositive electrode mixture pellets 2. Since the tip of tubular separator35 is wound in a hollow condition with no winding rod 33 at its center,tubular separator 35 is pressed by step 38 and thereby inserted intobattery casing 1; furthermore, when it is pressed against the bottomface of battery casing 1, this tip is squeezed inwards. Then, by furtherpressure applied by the tip of winding rod 33, the bending produced bythis squeezing is molded into a flat condition, forming bottom part 35 a(see FIG. 9). After this, winding rod 33 is released from tubularseparator 35 by backwards rotation and raised, while battery feed jig 15is lowered, so that tubular separator 35 is left in a condition in whichit is installed in battery casing 1.

Battery casing 1 with tubular separator 35 installed therein is then fedto the next step by battery feed jig 15 and, as shown in FIG. 10C, ismoved below bottom separator installation device 39. Bottom separatorinstallation device 39 is provided with an insertion rod 40 andinsertion guide hole 41; when bottom separator 36 that has been cut tocircular shape is supplied to above insertion guide hole 41, insertionrod 40 is lowered. Simultaneously, battery feed jig 15 is raised and theopen end of battery casing 1 is brought into contact with a locatingelement 42 of bottom separator installation device 39. Since insertionguide hole 41 is formed of cylindrical shape of smaller diameter thanthe diameter of bottom separator 36, when bottom separator 36 isinserted into insertion guide hole 41 by insertion rod 40, thecircumferential region of bottom separator 36 is raised, forming aflat-bottomed U-shape in cross-section. When insertion rod 40 is furtherlowered, as shown in FIG. 10D, bottom separator 36 is installed onbottom part 35 a produced by squeezing in of the bottom end of tubularseparator 35.

After undergoing the steps of insertion of tubular separator 35 andbottom separator 36, battery casing 1 is fed to the subsequent steps(not shown) to complete the alkaline dry battery 30.

However, the battery construction and its manufacturing steps in theprior art described above were subject to the following problems.

(1) The bottom end part of tubular separator 35 was squeezed inwards toform bottom part 35 a and further, in order to block the apertureproduced in the middle of bottom part 35 a, this aperture portion wasclosed by placing on bottom part 35 a a bottom separator 36. Because ofthis, since a double-layer structure is adopted in which, in addition tothe folding-over produced by squeezing of the bottom part 35 a, bottomseparator 36 is overlaid thereon, the thickness of the separator portionis increased, resulting in the production of a step (offset in the axialdirection) in the reaction surfaces of negative electrode gel 4 andpositive electrode mixture pellets 2 that face each other throughtubular separator 35. Even though, as described above, a step 1 a isprovided in the bottom face of battery casing 1, this is stillinsufficient to eliminate the step previously referred to. Furthermore,the discharge performance of the battery is lowered due to thediminution in capacity to receive the negative electrode gel.

(2) In addition to the overlapping in pleated form of the bottom part 35a produced by the squeezing of the bottom end part of tubular separator35, due to the double-layer construction with bottom separator 36, aconstruction is produced in which the separator portion at the bottom ofbattery casing 1 is resistant to deformation. As a result, if thenegative electrode gel 4 is caused to expand by over-discharging, sincethis expansion force cannot escape at the bottom, the internal pressureproduced by the expansion acts on the sealing plate 7, risking failureof the thin part 7 a provided in sealing plate 7. The purpose of theprovision of this thin part 7 a is, in the first place, to preventbursting of the battery if the internal pressure rises abnormally due tomis-use such as mixing new and old batteries or inserting the wrong wayround, and its failure due to expansion of negative electrode gel 4produced by over-discharging must be avoided.

(3) Since bottom separator 36 is arranged in contact with negativeelectrode gel 4, which is liable to flow, it can easily be displaced byflow of negative electrode gel 4 if the battery is subjected to shock orvibration. Internal short-circuiting due to displacement of bottomseparator 36 can therefore easily occur.

(4) In the step of inserting bottom separators 36 into battery casings 1by means of bottom separator installation device 39, bottom separators36 pre-cut to prescribed dimensions and arranged in a stack are suppliedby being picked up, one at a time, by vacuum suction. With this method,thin bottom separators 36 cannot be employed, but, when the thickness ofbottom separator 36 is large, discharge performance is adverselyaffected, as described in paragraph (1) above.

(5) Since tubular separator 35 and bottom separator 36 are installed inbattery casing 1 in separate steps, the number of steps is increased andproductivity lowered, and the size of the manufacturing equipmentbecomes large.

The present invention has been devised in order to solve theaforementioned problems of the prior art, its object being to provide amethod of manufacturing and device therefor whereby a cylindricalbattery of high battery performance and reliability can be manufacturedin an efficient manner.

DISCLOSURE OF THE INVENTION

A cylindrical battery according to the present invention comprises: abattery casing formed in a cylindrical shape having a bottom and havinga projection protruding outwards in the middle of the bottom face;positive electrode mixture pellets formed in cylindrical shape andaccommodated in said battery casing; a tubular separator formed incylindrical shape; negative electrode gel accommodated on an inner sideof the positive electrode mixture pellets with said tubular separatorinterposed therebetween; a bottom separator arranged at the bottom faceon the inside of said battery casing; and a sealing plate that seals theopen end of said battery casing; wherein said bottom separator is formedin the form of a sheet of thickness less than that of said tubularseparator and of dimensions larger than the diameter of tubularseparator, being arranged such that a peripheral part thereof is raisedat the outside of tubular separator, thereby isolating said negativeelectrode gel and the battery casing.

With a construction as described above, the capacity to receive thenegative electrode gel is increased since the tubular separator isformed without squeezing-in in the inwards direction at its bottom end,and the bottom part of the negative electrode gel and the inner bottomface of the battery casing are separated merely by a thin bottomseparator; also, the discharge performance of the battery is improvedsince the reaction area where the positive electrode mixture pellets andnegative electrode gel face each other is increased. Also, since thethin bottom separator is easily deformed and a space formed by a recessin the bottom face of the battery casing is provided at theunder-surface of the bottom separator, if the negative electrode gelswells up due to over-discharging etc., this expansion can be absorbedby deformation of the bottom separator towards the space of this recess.Consequently, liquid leakage from the internal pressure release portformed in the sealing plate caused by rise of internal pressure producedby swelling-up of the negative electrode gel can be prevented. Also,since the bottom end of the tubular separator is surrounded from theoutside by the peripheral raised portion of the bottom separator, beingin a condition sandwiched between the tubular separator and the positiveelectrode mixture pellets, even if large impacts or vibration areapplied to the battery, there is no possibility of the bottom separatorbeing shifted out of position, so leakage of negative electrode gelcaused by displacement of the bottom separator from its position can beprevented and there is thus no possibility of internal short circuitsarising.

With a cylindrical battery according to the present invention, thebottom separator that isolates the negative electrode gel and batterycasing consists of a thin sheet of thickness 0.03 to 0.2 mm; thus,compared with the thick separator of double-layer construction used inthe prior art, the accommodation capacity for the negative electrode gelis increased and the reaction area is also increased. Also, due to thisthinness, the bottom separator can easily be deformed, so if thenegative electrode gel swells up on over-discharging, it can deformtowards the space constituted by the recess formed at the bottom face ofthe battery casing, thereby absorbing this expansion. If the thicknessof the bottom separator is less than 0.03 mm, it is difficult toconstruct a uniform thin film and strength is lowered. On the otherhand, if the thickness is greater than 0.2 mm, the effect of absorbingexpansion by deformation is lowered, so a thickness within this range isappropriate.

Also, since the bottom separator in a cylindrical battery according tothe present invention is formed using an ion-permeable sheet, eventhough its peripheral raised portion is interposed between the positiveelectrode mixture pellets and negative electrode gel, the reaction ofthese two is not impeded.

Also, since the bottom separator in a cylindrical battery according tothe present invention is formed in rectangular shape, the loss involvedin cutting it out from the paper stock can be eliminated and since nocutting-out waste is therefore produced, the time required to dispose ofsuch waste can be eliminated.

In a method of manufacturing a cylindrical battery that is manufacturedby inserting positive electrode mixture pellets formed in cylindricalshape into a cylindrical casing having a bottom, inserting a tubularseparator so as to contact the inner circumferential surface of saidpositive electrode mixture pellets, inserting a bottom separator at thebottom face of battery casing, injecting a negative electrode gel intothe central space enclosed by the two separators and, and sealing theopen end of the battery casing by means of a sealing plate; according tothe invention, said bottom separator is formed in the form of a sheet ofdimensions larger than the diameter of the tubular separator and bothseparators are inserted simultaneously into the battery casing with theleading end of the tubular separator in contact with this bottomseparator, thereby inserting both separators into the battery casingwith the peripheral portion of the bottom separator raised so that theleading end of the tubular separator is surrounded from the outside bythe raised portion at the periphery of said bottom separator.

With the method of manufacture described above, the tubular separatorand bottom separator can be simultaneously inserted into the batterycasing, so the steps of inserting both separators can be combined intoone, enabling production efficiency to be raised. Also, since the bottomseparator is inserted into the battery casing with the leading end ofthe tubular separator surrounded from outside by the peripheral raisedportion of the bottom separator, even if the battery is subjected toimpacts or vibration, the bottom separator cannot easily be displacedfrom its position. Furthermore, since the portion of the negativeelectrode gel nearest the bottom face is separated from the batterycasing only by the bottom separator, the capacity for negative electrodegel is increased and no step is produced in the reaction face with thepositive electrode mixture pellets, so discharge performance can beimproved.

Also, in a device for manufacturing a cylindrical battery according tothe present invention whereby a cylindrical battery is manufactured byinserting positive electrode mixture pellets formed into cylindricalshape into a cylindrical battery casing having a bottom, then insertinga tubular separator so as to contact the inside circumferential face ofsaid positive electrode mixture pellets and inserting a bottom separatoron to the bottom face of battery casing, and injecting a negativeelectrode gel into the central space enclosed by the separators,comprising: a separator insertion jig including a circular guide holealong whose central axis a tubular separator is passed, a cylindricalpart which is below this guide hole and that can be inserted into theopen end of battery casing, and a holding part that is above said guidehole, for holding the bottom separator; bottom separator supply meanswhereby a bottom separator cut to dimensions larger than the diameter ofthe tubular separator is supplied into the holding part of saidseparator insertion jig; and separator installation means having awinding rod and whereby a tubular separator is formed by windingseparator paper on to this winding rod, and whereby this tubularseparator is inserted into the battery casing through said guide holetogether with the bottom separator held within the holding part of saidseparator insertion jig; the separator insertion jig to which the bottomseparator has been supplied from said bottom separator supply means, thewinding rod of the separator installation means on which a tubularseparator has been formed, and the battery casing into which thepositive electrode mixture pellets have been inserted are positionallylocated such that their respective central axes coincide with anidentical line; the cylindrical part of the separator insertion jig isfitted onto the open end of the battery casing; and said separatorinsertion jig, winding rod, and battery casing are relatively moved suchthat the winding rod is inserted into the battery casing through saidguide hole and is then once more returned to said positionally locatedcondition, whereby the tubular separator and the bottom separator aresimultaneously installed in the battery casing.

With the manufacturing device described above, the separatorinstallation means holding a tubular separator which has been wound onto a winding rod, and the battery casing are respectively located inposition above and below the separator insertion jig, which has aholding part, guide hole, and cylindrical part, and the open end of thebattery casing is fitted on to the cylindrical part of the separatorinsertion jig; the winding rod of the separator installation means isthen advanced into the battery casing through the holding part and guidehole of the separator insertion jig. Since the bottom separator issupplied beforehand into the holding part and the tubular separator onthe winding rod pushes the bottom separator into the guide hole by meansof its tip, the peripheral portion of the bottom separator is raised upand assumes a condition surrounding the tip of the tubular separatorand, in this condition, both separators are simultaneously inserted intothe battery casing. Since the tubular separator wound on to the windingrod is inserted into the battery casing from the guide hole of theseparator insertion jig through its cylindrical part, its wound-upcondition is not released until it is inserted into the battery casingi.e. the wound-up condition is only released, by its own spring-backeffect, once it has been inserted into the battery casing. It thenadheres tightly to the previously inserted positive electrode mixturepellets and is released from the winding rod. At this point, the tubularseparator can easily be released by rotating the winding rod in theopposite direction to the winding direction. Installation of the twoseparators is thus simultaneously completed by raising the winding rodfrom which the tubular separator has been released and lowering thebattery casing so that it is released from the cylindrical part of theseparator insertion jig.

Since the bottom separator supply means in the manufacturing devicedescribed above transfers the bottom separator to the separatorinsertion jig holding it by vacuum suction immediately after this bottomseparator has been cut off from the paper stock, it is possible toeffect feed of bottom separators one at a time in a manner linked to theoperation of the separator installation step. With the conventionalmethod, in which bottom separators are cut out beforehand and kept inreadiness, the small, light and thin bottom separators are difficult tohandle and it is difficult to achieve reliable vacuum suction of oneseparator at a time from the stack of separators. However, with thepresent invention, by providing the bottom separator cutting-out devicein the bottom separator supply means, the step of processing a smallpart which is difficult to handle can be eliminated.

Furthermore, the bottom separators in the manufacturing device describedabove are cut out into square shape from the paper stock, so they may becut from tape-shaped paper stock of width equal to the length of oneside of the square shape; in this way, cutting waste is not produced andloss of material is eliminated. Also, the cutting-out device itself canbe constructed in a straightforward manner.

Furthermore, as the holding part of the separator insertion jig in themanufacturing device described above comprises an accommodating spaceformed in circular shape having an internal diameter about the same asthe diagonal length of the square-shaped bottom separators, and aninsertion hole having a diameter smaller than the diagonal length of thebottom separators and opening at the top of this accommodating space,when a square bottom separator is inserted into the accommodating spacefrom the insertion hole, although the corner parts of the square shapeare deformed, since the internal diameter of the circular accommodatingspace is formed approximately equal to the diagonal length of the squareshape, when the bottom separator is inserted into the accommodatingspace, it returns to a flat condition, being automatically located inposition such that the corner parts contact the inner circumferentialsurface of the accommodating space. Also, holding and positionallocation of a small, light and thin bottom separator can easily beachieved without its position being displaced by the effects of aircurrents and/or vibrations produced by movement of the separatorinsertion jig.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partially sectioned front view showing the construction ofan alkaline dry battery according to an embodiment of the presentinvention;

FIG. 2 is a partially sectioned view showing the condition in which thetubular separator and bottom separator are installed in this battery;

FIG. 3 is a partially sectioned view showing the condition in whichexpansion has occurred of the negative electrode gel in this battery;

FIG. 4 is a partially sectioned view showing a modified example of theshape of the battery casing of this battery;

FIGS. 5A-5C are partially sectioned diagrammatic side views showing thesequence of steps of bottom separator supply in a device formanufacturing the above battery;

FIG. 6 is a plan view showing the construction of a separator insertionjig in the above manufacturing device;

FIG. 7 is a cross-sectional view seen along the line VII—VII of FIG. 6;

FIGS. 8A-8D are partially sectioned diagrammatic side views showing thesequence of steps of separator insertion in this manufacturing device;

FIG. 9 is a partially sectioned front view showing a prior artconstruction of an alkaline-manganese dry battery; and

FIGS. 10A-10D are partially sectioned diagrammatic side views showingthe sequence of steps of separator installation in a prior artmanufacturing device.

BEST MODE FOR CARRYING OUT THE INVENTION

The construction of an alkaline dry battery (cylindrical battery)according to an embodiment of the present invention is described belowwith reference to FIG. 1 to FIG. 4. Elements which are common to theprior art construction are given the same reference numerals.

In FIG. 1, alkaline dry battery 10 in this embodiment is constituted byaccommodating in battery casing 1, in order from the outside, positiveelectrode mixture pellets 2, tubular separator 3 and bottom separator 5,and negative electrode gel 4, the open end of battery casing 1 beingsealed by sealing plate 7 and negative electrode terminal 8 beingconnected to negative electrode current collector 9 inserted intonegative electrode gel 4. Battery casing 1 is of a type which isintegral with the positive electrode terminal and is formed with arecess in the bottom face within the casing, which is of cylindricalshape having a bottom, such that a positive electrode projection 6projects outwards. As shown to a larger scale in FIG. 2, bottomseparator 5 which is arranged at the bottom of this alkaline dry battery10 has a raised part 5 a and, thanks to this raised part 5 a, isconstituted such as to enclose from outside the lower end of tubularseparator 3 which is formed in cylindrical shape, and prevents internalshort circuits by isolating negative electrode gel 4 and battery casing1 constituting the positive electrode terminal of the battery.

Tubular separator 3 is formed in cylindrical shape by winding, so as toconstitute four layers, separator paper made of chemical fiber non-wovencloth. In contrast, bottom separator 5 is formed using fine porous filmthat permits the passage of ions only. In this embodiment, a bottomseparator 5 is employed produced by cutting into square shape separatorpaper of thickness 0.03 to 0.2 mm made by laminating non-woven cloth onto both sides of cellophane, the length of one side of which is greaterthan the diameter of tubular separator 3. It would be possible to cutbottom separator 5 into circular shape, in which case however, there isa lot of loss when cutting out from the paper stock (hoop stock); thearea corresponding to this loss is left behind as cutting-out waste,which requires labor to dispose of; cutting into rectangular form istherefore desirable.

Thanks to the above construction, the under-surface of negativeelectrode gel 4 and the bottom face of battery casing 1 are in acondition separated only by a thin bottom separator 5, so no step(offset condition in the axial direction) is produced in theelectromotive reaction surfaces of the positive electrode mixturepellets 2 and negative electrode gel 4, which face each other throughtubular separator 3, as shown; furthermore, the receiving capacity fornegative electrode gel 4 can be increased, so discharge performance canbe improved. Although the raised part 5 a of bottom separator 5 isinterposed between tubular separator 3 and positive electrode mixturepellets 2, since, as mentioned above, bottom separator 5 consists ofion-permeable film, thanks to ionic conduction, there is no possibilityof the electromotive reaction being impeded.

Also, since the thickness of bottom separator 5 is small, at 0.03 to 0.2mm, and a space formed by positive electrode projection 6 is present atits under-surface, when negative electrode gel 4 expands due toover-discharging, as shown in FIG. 3, expansion of negative electrodegel 4 is absorbed by deformation of bottom separator 5 towards thisspace. Consequently, liquid leakage due to failure of thin part 7 a ofsealing plate 7 caused by rise of internal pressure produced byexpansion of negative electrode gel 4 can be prevented. If the bottomseparator 5 is thicker than 0.2 mm, its action of absorbing expansion ofnegative electrode gel 4 by means of such deformation is notsufficiently manifested. Also, if it is thinner than 0.03 mm, it isdifficult to obtain a uniform thin film, and sufficient strength isdifficult to achieve. Thin part 7 a is provided with the object ofpreventing bursting of the battery by releasing internal pressure to theoutside by failing when there is an extraordinary rise in internalpressure due to mis-use such as short-circuiting of the battery orinverted insertion and it is undesirable that it should be broken byexpansion of negative electrode gel 4. However, the above constructionacts effectively in that the under-surface of negative electrode gel 4is separated from battery casing 1 only by a thin bottom separator 5, sofailure of thin part 7 a caused by expansion of negative electrode gelis prevented.

Also, since the bottom end of tubular separator 3 is arranged such thatit is wrapped from the outside by the raised part 5 a at its periphery,this raised part 5 a being in a condition in which it is gripped betweentubular separator 3 and positive electrode mixture pellets 2, there isno possibility of displacement of bottom separator 5 due to flow ofnegative electrode gel 4 when subjected to large shocks such as if thebattery is dropped or on being subjected to vibration duringtransportation; as a result, internal short circuits due to leakage ofnegative electrode gel 4 are prevented.

It should be noted that, although, in this embodiment, battery casing 1was formed as a positive electrode-integrated type, even in the case ofa battery casing of the type wherein the positive electrode terminal isseparate, the positive electrode terminal being separately attachedcovering a raised part in which the casing under-surface projectsoutwards, since a space is present where this raised part is formed,this can be utilized as a space for absorbing expansion of the negativeelectrode gel.

As described above, with the construction of the cylindrical batteryaccording to the present invention, no squeezing inwards takes place atthe bottom of tubular separator 3 as it does in the case of theconventional construction, so the bottom portion of negative electrodegel 4 is separated from battery casing 1 only by thin bottom separator5; as a result, a battery casing 1 can be formed without providing astep 1 a such as was described in the description of the prior artconstruction. That is, as shown in FIG. 4, the bottom face of batterycasing 1 can be made of a shape without a step 1 a, in which onlypositive electrode projection 6 projects outwards. Even in this case,since bottom separator 5 is thin, no large step is produced in thereaction surfaces where the negative electrode gel 4 and positiveelectrode mixture pellets 2 face each other.

Next, the construction of a manufacturing device whereby an alkaline drybattery 10 of the above construction is manufactured will be describedbelow with reference to FIG. 5 to FIG. 8.

In FIG. 5A, bottom separator paper 16 prepared as hoop stock ofthickness 0.03 to 0.2 mm by laminating non-woven cloth on to both facesof cellophane is pulled out to a cutting position, and punched out by aThompson mold 17 into a square shape of prescribed dimensions tomanufacture bottom separator 5. A bottom separator 5 that has been thuscut out is immediately held by suction by a suction nozzle (bottomseparator supply means) 18 and transferred to a separator insertion jig11, as shown in FIGS. 5B, 5C. Since in this way bottom separators 5 aretransferred by suction nozzle 18 immediately after being cut from bottomseparator paper 16, even thin bottom separators 5 can be reliably held,one sheet at a time, by suction nozzle 18. Also, since the width of thebottom separator paper stock 16, which is in the form of a tape, isequal to the length of one side of bottom separator 5 that is cut intosquare shape, there is no loss of material when bottom separator 5 iscut into square shape from this bottom separator paper stock 16, socutting waste is not produced and the task of disposing of this wastecan be eliminated. Furthermore, although the Thompson mold 17illustrated is of the reciprocatory type, an arrangement could of coursebe adopted in which a rotary Thompson mold is employed.

As shown in FIG. 6 and FIG. 7, separator insertion jig 11 has a circularguide hole 20 in a central position and is formed with a cylindricalpart 21 at the bottom of guide hole 20, having a diameter such that itcan be inserted into the open end of battery casing 1. At the top ofguide hole 20, there is provided a holding part 22 having a diametercorresponding to the length of the diagonal of square-shaped bottomseparator 5 and defining a space whereby bottom separator 5 can beaccommodated in a flat condition. In addition, at the top of holdingpart 22, there is provided an insertion hole 23 having a diametershorter than the length of the diagonal of bottom separator 5.

As shown in FIG. 7, when bottom separator 5 held on suction nozzle 18 isinserted into holding part 22 from insertion hole 23, the corners of thesquare shape are deformed, but, since the accommodating space of holdingpart 22 has a sufficient height dimension, when inserted into theaccommodating space, the corners of this deformed bottom separator 5 canreturn to the original shape. In this way, a bottom separator 5 that isinserted into the space of holding part 22 assumes a flat conditionblocking guide hole 20, and the center of guide hole 20 and the centerof bottom separator 5 automatically coincide. Moreover, since thediameter of insertion hole 23 is smaller than the internal diameter ofholding part 22, there is no possibility of even a thin and light bottomseparator 50 jumping out of holding part 22 or being mis-positioned byvibration or air currents. Consequently, even if separator insertion jig11 with a bottom separator 5 inserted in holding part 22 is moved,bottom separator 5 is held in stable fashion maintained in theprescribed position.

When bottom separator 5 is transferred, separator insertion jig 11 ismoved below separator installation device (separator installation means)12, as shown in FIG. 8A. Battery feed jig 15 holding a battery casing 1which has already received in a previous step, not shown, positiveelectrode mixture pellets 2, is then moved to below this separatorinsertion jig 11. Separator insertion jig 11 and battery feed jig 15 atthis point are located in position such that the respective central axesof separator insertion jig 11 and battery casing 1 coincide with thecentral axis of winding rod 13 of separator installation device 12.

Separator installation device 12 comprises: a winding rod 13 which isdriven in rotation in the forwards and reverse directions, a windingguide 19 arranged with the provision of a gap corresponding to thethickness of the tubular separator 3 between this and the surface ofwinding rod 13, and a winding roll 14 which roll presses against thetubular separator paper wound on to the winding rod 13 such that nowinding slackness is produced. As shown in FIG. 8D, winding rod 13comprises a base rod 13 b and a winding part 13 a therebelow on whichtubular separator paper is wound, a step 24 being provided at the bottomend of base rod 13 b so that the diameter of winding part 13 a is formedsmaller than the diameter of base rod 13 b by an amount corresponding tothe thickness of tubular separator 3. Also, a bottom separatorinstallation part 13 c having a diameter smaller than the diameter ofwinding part 13 a by an amount corresponding to the thickness of bottomseparator 5 is formed at the lower end of winding part 13 a.

In FIG. 8A, when tubular separator paper that has been cut to theprescribed dimensions is supplied between winding rod 13 and windingguide 19, tubular separator paper is wound a prescribed number of timeswhilst winding rod 13 is rotated in the winding direction and windingroll 14 is being pressed against winding rod 13, thereby forming onwinding rod 13 a tubular separator 3 in a cylinder shape of prescribedthickness.

Next, winding roll 14 is removed from winding rod 13 and winding rod 13is lowered. At this point, as shown in FIG. 8B, battery feed jig 15 israised, so that the cylindrical part 21 of separator insertion jig 11 isinserted into the open end of battery casing 1, which is being held.When winding rod 13, on which tubular separator 3 is wound, passesthrough the insertion hole 23 of separator insertion jig 11, its tippushes out the middle portion of bottom separator 5 that is held inholding part 22, causing it to advance within guide hole 20 of separatorinsertion jig 11. As a result, tubular separator 3 is inserted intobattery casing 1 passing through guide hole 20 in a condition with theperipheral portion at its leading end surrounded by the peripheral partof bottom separator 5. Since winding rod 13 is formed with a bottomseparator installation part 13 c of somewhat smaller diameter at itsbottom end, even though the circumferential part of bottom separator 5surrounds the circumferential part of the leading end of tubularseparator 3, the leading end part that is surrounded by bottom separator5 and the other portions are molded to the same diameter by passage ofthe leading end of tubular separator 3 through guide hole 20. Whentubular separator 3 is inserted into the battery casing, tubularseparator 3 is held by winding guide 19 as the winding rod 13 descends,up to the time point where the leading end of tubular separator 3 entersguide hole 20 of separator insertion jig 11, so, right up to the end ofthe process, no slackening of the winding of tubular separator 3 canoccur. Tubular separator 3 that has penetrated into battery casing 1 ispushed by step 24 of winding rod 13 so that it is inserted until bottomseparator 5 comes into contact with the bottom face of battery casing 1.

As shown in FIG. 8C, when winding rod 13 descends to the position atwhich bottom separator 5 contacts the bottom face of battery casing 1,battery feed jig 15 holding battery casing 1 is lowered, while windingrod 13 is raised whilst rotating in the opposite direction to thedirection of winding. Due to the reverse rotation of this winding rod 13and the spring-back of tubular separator 3 itself, tubular separator 3is separated from winding rod 13 and adheres to the innercircumferential surface of positive electrode mixture pellets 2.

As shown in FIG. 8D, when winding rod 13 is raised to its originalposition, battery casing 1 in which tubular separator 3 and bottomseparator 5 have now been installed is fed to the next step, not shown,by battery feeding jig 15. Also, separator insertion jig 11 moves intothe condition shown in FIG. 5B to commence the operation of transferringthe next bottom separator 5, and separator installation device 12commences the operation of winding up the tubular separator 3.

As described above, with the manufacturing device for cylindricalbatteries according to the present invention, the tubular separator 3and bottom separator 5 are installed in battery casing 1 simultaneously,so the steps for insertion of the separators can be unified into asingle step; this makes possible improvement in productivity due toreduction in the number of steps and simplification of the manufacturingdevice.

Industrial Applicability

Since, with a cylindrical battery according to the present invention, athin bottom separator 5 is employed and squeezing tubular separator 3inwards at its bottom end is eliminated, the electromotive reaction areawhere the positive electrode mixture pellets 2 and negative electrodegel 4 face each other can be increased and the amount of negativeelectrode gel 4 accommodated can be increased, thereby making itpossible to improve the discharge performance of the battery. Also, evenif the battery is subjected to shock or vibration, bottom separator 5does not get out of position and furthermore if negative electrode gel 4expands, this expansion can be absorbed by deformation of the bottomseparator, thereby preventing liquid leakage or occurrence of internalshort-circuiting and so enabling the reliability of the battery to beimproved.

Furthermore, with the manufacturing device for a cylindrical batteryaccording to the present invention, since tubular separator 3 and bottomseparator 5 are simultaneously installed in battery casing 1 with thelower end of tubular separator 3 being put in a condition surrounded byraised part 5 a of bottom separator 5 from the outside thereof, thesteps of installing the separators can be unified into a single step,enabling productivity to be raised and the manufacturing device to besimplified.

What is claimed is:
 1. A cylindrical battery comprising: a batterycasing (1) formed in a cylindrical shape having a bottom and having aprojection protruding outwards in the middle of the bottom face;positive electrode mixture pellets (2) formed in cylindrical shape andaccommodated in said battery casing (1); a tubular separator (3) formedin cylindrical shape; negative electrode gel (4) accommodated on aninner side of the positive electrode mixture pellets (2) with saidtubular separator (3) interposed therebetween; a bottom separator (5)arranged at the bottom face on the inside of said battery casing (1);and a sealing plate (7) that seals the open end of said battery casing(1); wherein said bottom separator (5) is formed in the form of a sheetof thickness less than that of said tubular separator (3) and ofdimensions larger than the diameter of tubular separator (3), beingarranged such that a peripheral part thereof is raised at the outside oftubular separator (3), thereby isolating said negative electrode gel andthe battery casing (1).
 2. The cylindrical battery according to claim 1wherein the thickness of bottom separator (5) is 0.03 to 0.2 mm.
 3. Thecylindrical battery according to claim 1 wherein bottom separator (5)comprises an ion-permeable sheet.
 4. The cylindrical battery accordingto claim 1 wherein bottom separator (5) is formed in rectangular shape.5. A method of manufacturing a cylindrical battery that is manufacturedby inserting positive electrode mixture pellets (2) formed incylindrical shape into a cylindrical casing (1) having a bottom,inserting a tubular separator (3) so as to contact the innercircumferential surface of said positive electrode mixture pellets (2),inserting a bottom separator (5) at the bottom face of battery casing(1), injecting a negative electrode gel (4) into the central spaceenclosed by the two separators (3, 5), and sealing the open end ofbattery casing (1) by means of a sealing plate (7); wherein said bottomseparator (5) is formed in the form of a sheet of dimensions larger thanthe diameter of tubular separator (3) and both separators (3) and (5)are inserted simultaneously into battery casing (1) with the leading endof tubular separator (3) in contact with this bottom separator (5),thereby inserting both separators (3, 5) into the battery casing withthe peripheral portion of bottom separator (5) raised so that theleading end of tubular separator (3) is surrounded from the outside bythe raised portion at the periphery of said bottom separator (5).
 6. Adevice for manufacturing a cylindrical battery whereby a cylindricalbattery is manufactured by inserting positive electrode mixture pellets(2) formed into cylindrical shape into a cylindrical battery casing (1)having a bottom, then inserting a tubular separator (3) so as to contactthe inside circumferential face of said positive electrode mixturepellets (2) and inserting a bottom separator (5) on to the bottom faceof battery casing (1), and injecting a negative electrode gel (4) intothe central space enclosed by separators (3, 5), comprising: a separatorinsertion jig (11) including a circular guide hole (20) along whosecentral axis a tubular separator (3) is passed, a cylindrical part (21)which is below this guide hole (20) and that can be inserted into theopen end of battery casing (1), and a holding part (22) that is abovesaid guide hole (20), for holding bottom separator (5); bottom separatorsupply means (18) whereby a bottom separator (5) cut to dimensionslarger than the diameter of tubular separator (3) is supplied intoholding part (22) of said separator insertion jig (11); and separatorinstallation means (12) having a winding rod (13) and whereby a tubularseparator (3) is formed by winding separator paper on to this windingrod (13), and whereby this tubular separator (3) is inserted intobattery casing (1) through said guide hole (20) together with the bottomseparator (5) held within holding part (22) of said separator insertionjig (11); wherein separator insertion jig (11) to which the bottomseparator (5) has been supplied from said bottom separator supply means(18), the winding rod (13) of the separator installation means (12) onwhich a tubular separator (3) has been formed, and the battery casing(1) into which the positive electrode mixture pellets (2) have beeninserted are positionally located such that their respective centralaxes coincide with an identical line; the cylindrical part (21) of theseparator insertion jig (11) is fitted onto the open end of the batterycasing (1); and said separator insertion jig (11), winding rod (13), andbattery casing (1) are relatively moved such that the winding rod (13)is inserted into the battery casing (1) through said guide hole (20) andis then once more returned to said positionally located condition,whereby the tubular separator (3) and the bottom separator (5) aresimultaneously installed in the battery casing (1).
 7. The device formanufacturing a cylindrical battery according to claim 6 wherein thebottom separator supply means (8) is constructed such that, immediatelyafter a bottom separator (5) has been cut from paper, said bottomseparator (5) is transferred to the separator insertion jig (11) bybeing held by vacuum suction.
 8. The device for manufacturing acylindrical battery according to claim 6 wherein the bottom separators(5) are cut into square shape from paper.
 9. The device formanufacturing a cylindrical battery according to claim 6 wherein saidseparator insertion jig (11) further comprises an insertion hole (23) ofaperture diameter shorter than the length of the diagonal of bottomseparator (5) that has been cut into square shape, and said holding part(22) is formed with a circular accommodating space whose internaldiameter is of practically the same length as the diagonal length ofbottom separator (5) that has been cut to square shape.